Nozzles for a cleaning installation of a printing machine

ABSTRACT

The nozzle has a channel ( 24 ) in which a cleaning solution is injected under pressure, and an outlet ( 26 ) through which the solution is sprayed against a cylinder. The outlet ( 26 ) is formed by a first part ( 23 ) and a second part ( 25 ), said second part ( 25 ) being movable with respect to said first part ( 23 ) in order to vary the size of said outlet ( 26 ).

The present invention concerns a nozzle for a cleaning installation usedto clean the wiping cylinder of a printing machine.

Cleaning installations for printing machines are known in the art. Forexample, U.S. Pat. No. 5,390,598 discloses a wiping device for anintaglio printing machine comprising a wiping cylinder and aninstallation for the continuous cleaning of said cylinder. The principleand basic technical features of the wiping device as disclosed in thispatent are incorporated by reference to the present application. Theinstallation comprises a container for receiving the cleaning liquidwhich continuously acts on the wiping cylinder and cleaning elements incontact with the periphery of the wiping cylinder comprising, in thedirection of rotation of the cylinder, brushes and/or wiping blades andat least a row of nozzles parallel to the axis of the wiping cylinder,the nozzles being arranged to eject the cleaning liquid into the regionof contact of the cleaning elements with the wiping cylinder. There maybe one or several rows of spray nozzles, which send a cleaning solutionunder pressure. Known cleaning solutions are disclosed for example inU.S. Pat. No. 5,855,787 or in European patent application N^(o) 0 927632, the content of which is incorporated by reference in the presentapplication.

U.S. Pat. No. 4,236,450 discloses another cleaning installation for thecontinuous cleaning of a wiping roller of a printing machine, theprinciples of which are incorporated by reference in the presentapplication. This installation is characterized in that it comprises atleast two rows of nozzles arranged parallel to the axis of the wipingroller, the nozzles spraying the cleaning solution onto the surface ofthe wiping cylinder. An example of a nozzle disclosed in this patentcomprises a plate pressed against a wall of a support, said platecomprising small grooves in order to spray a continuous film of liquid.All the rows of nozzles are connected to pumps, which supplies them withcleaning liquid.

In another embodiment known in the art, the nozzles are made of a shaftof rectangular section comprising an inner channel parallel to the axisof the shaft, in which the wiping solution is sent under pressure, andan array of holes forming the nozzles, which are formed on the side ofthe shaft facing the wiping roller. Said holes are in communication withsaid channel in order for the solution to be sprayed against the wipingroller with a given pressure.

The problem encountered in the known installations is the fact that thenozzles, which have a small diameter, may be blocked or obturated byparticles present in the cleaning solution so that the cleaning effectis reduced. In such case, it becomes necessary to stop the printingmachine, remove the wiping cylinder to gain access to the shafts withthe nozzles and to remove said shafts from the machine to be able toclean the nozzles in a remote place. Once this has been done, the shaftsmust be assembled and adjusted in the machine and then only can thewiping cylinder brought back in position. All these operations are timeconsuming and, since the machine is not working anymore, they have animportant cost.

It is therefore an object of the present invention to improve the knowninstallations.

Another aim of the invention is to provide a cleaning installation thatis easy to clean in the event of an obturated nozzle.

Another aim of the invention is to provide an improved nozzle designthat may be cleaned in a simple an effective manner.

A nozzle according to the invention is defined in independent claim 1 ofthe present application.

Dependent claims 2 to 5 define particular embodiments of the nozzleaccording to the invention.

Claim 6 and 7 define a cleaning installation comprising nozzlesaccording to the invention.

Independent claim 8 defines a printing machine comprising a cleaninginstallation according to the invention.

The invention will be best understood with the description of severalembodiments and the accompanying drawings in which:

FIG. 1 discloses a diagrammatic side view, partly in section, of awiping installation in a printing machine.

FIG. 2 shows the principle of an array of cleaning nozzles.

FIG. 3 shows the principle of a nozzle according to the invention.

FIG. 4 shows an embodiment of a nozzle according to the invention.

FIG. 5 shows a top view of the nozzle of FIG. 4.

The installation represented in FIG. 1, as an example of a cleaninginstallation, corresponds to the one disclosed in U.S. Pat. No.4,236,450, the description of which is incorporated by reference in thepresent application. In this installation, a wiping roller 1 rotatingabout a shaft 1 a in the direction of the arrow F1 is in contact with aplate-supporting cylinder 2 of a printing machine. The wiping roller 1is located partly inside a container 3 in which the cleaninginstallation is mounted. This installation comprises also severalcleaning members formed by scrapers 4, 5 and brushes 6. The cleaningmembers extend over the entire length of the wiping roller 1 and act onits periphery to remove the major part of the ink mechanically from theperiphery of this roller. The installation comprises also rows ofnozzles 7, 8, 9, 10, 11 and 12 parallel to the axis of the wiping roller1 for ejecting a cleaning solution, such as disclosed for example inU.S. Pat. No. 5,855,787 or in European patent application N^(o) 0 927632, onto the periphery of the roller 1 in front of the area of thescrapers 4, 5 and of brushes 6 which are in contact with the roller 1.

The first row of nozzles 7 (according to the direction of rotation ofthe roller 1) is located in front of the first scraper 5 making itpossible to wet the wiping roller with a continuous film of cleaningsolution. The first scraper 5 removes approximately 95% of the mass ofink adhering to the surface of the wiping roller and in order that theparticles of ink do not accumulate behind this scraper 5, the second rowof nozzles 8 is mounted on a scraper support 13 behind said scraper 5.The other rows of nozzles 9 to 12 are mounted on the scraper supports14. The rows of nozzles 7 to 12 are connected to the outlet of pump 19,which supplies them with cleaning solution coming from source 15 throughpipe 16 and distributor 17 feeding the rows of nozzles 7-12 with thecleaning solution.

The principle of an array of nozzles as used in the installation of FIG.1 and according to the invention is described with reference to FIG. 2.The system comprises preferably a tank 18 of cleaning solution,corresponding to the source 15 of FIG. 1, with a pump 19, a valve 20 anda distributing shaft 21 supporting an array of nozzles 22.

The principle of a nozzle according to the invention is described morespecifically with reference to FIG. 3. The nozzle comprises a first part23 attached to the distributing shaft 21 in which the cleaning solutionis brought under pressure P1 in the channel 24. The nozzle comprises asecond part 25, which is mobile with respect to the first part 23, therelative position of said mobile part 25 with respect to the first part23 defining the outlet channel 26 of the cleaning solution. The mobilepart 25 is pressed against the first part 23, which is schematised byspring 27 producing force Fs. Under working conditions, the cleaningsolution is brought under a given pressure P1 by pump 19 in the channel24, and this pressure is sufficient to counteract the force Fs of thespring, thus opening the outlet 26 until the forces are balanced betweenpressure P1 and force Fs.

If the outlet 26 is blocked by particles, then one increases thepressure P1 of the cleaning solution by pump 19 in order to push themobile part 25 against the spring element 27 outwards thus increasingthe size of the outlet 26, which then allows the blocking particles tobe ejected from the nozzle, by combination of higher pressure andincreased outlet size.

Such a procedure may be carried out on a regular basis, after a certaintime, or in case of an effective blockage of one or several nozzles.

Preferably, the first part 23 comprises stopping means for the mobilepart 25 so that the outlet 26 is never closed but retains its workingsize when no cleaning solution is injected. Accordingly, when a cleaningsolution is injected under pressure P1, the mobile part 25 does not movesince the outlet 26 already has its working size. Only when the pressureis increased, for example to clean the nozzles, is mobile part 25displaced thus increasing the size of the outlet 26 until the forcescreated by the increased pressure of cleaning solution and the spring 27element are balanced.

Further, the nozzle may comprise additional cleaning means in the shapeof a cleaning opening 28 which receives for example air under pressureat a pressure P2 through compressed air supply 29 which then is mixed tothe cleaning solution exiting from channel 24. This combination brings amore effective cleaning system with the combination of cleaning solutionand air.

An embodiment of a nozzle according to the invention is described withreference to FIGS. 4 and 5. The nozzle comprises said first part 23mounted, for example with a screw 30, on the distributing shaft 21 witha channel 24 for delivering the cleaning solution. This part of thenozzle may be made of two different parts attached together (shaft 21and part 23), as described here above, or in one single piece.

The first part 23 comprises an outlet 26 through which the cleaningsolution is injected against the wiping roller according to theprinciple of the invention (see FIG. 1). The nozzle further comprises anelastic blade 31 corresponding to the mobile part 25 of FIG. 3. Theblade 31 is mounted on the shaft 21 as shown by a screw 32 or otherequivalent means. As shown in FIG. 5, a top view of FIG. 4, when nocleaning solution is injected through outlet 26 or when the solution isinjected at working pressure, the blade 31 forms the nozzle which hasbeen shaped in first part 23, by remaining in contact with said firstpart 23. When it becomes necessary to clean a nozzle or several nozzles,the pressure of the cleaning solution for the wiping cylinder 1 isincreased thus increasing the size of the outlet 26 by moving blade 31away of first part 23.

As represented in FIG. 3, the nozzle of FIG. 4 may comprise additionalcleaning means 28, 29 bringing air under pressure in the nozzle which ismixed to the cleaning solution.

Several nozzles as the one disclosed in FIGS. 4 and 5 may be mounted onthe shaft 21, as represented schematically in FIG. 2, forming an arrayof cleaning nozzles.

Such a shaft 21 with an array of nozzles may be then mounted in theinstallation represented in FIG. 1. In this installation of FIG. 1,several parallel shafts 21 would then be placed next to each other withtheir longitudinal axis parallel to the shaft 1 a supporting the wipingcylinder 1, as the represented nozzles 7-12, thus spraying the cleaningsolution on the entire length of the wiping cylinder 1. This forms acleaning installation suitable for a printing machine, schematicallyrepresented in FIG. 1.

The embodiment disclosed in the present application are given by way ofexample are not interpreted as limiting the scope of the claims.

1. A cleaning installation for a printing machine comprising at leastone distributing shaft supporting an array of nozzles for cleaning awiping cylinder of the printing machine, each nozzle having a channel inwhich a cleaning solution is injected under pressure, and an outletthrough which the solution is sprayed against the cylinder,characterised in that wherein the outlets of said nozzles are formed bya first part, which is mounted on or which is part of the distributingshaft, and by a second part which is movable with respect to said firstpart in order to vary the size of said outlet and allow a cleaning ofsaid array of nozzles by moving said second part away of said firstpart.
 2. A cleaning installation according to claim 1, wherein saidsecond part is pressed against said first part by elastic means.
 3. Acleaning installation according to claim 1, wherein said second part isformed by a blade.
 4. A cleaning installation according to claim 3,wherein said blade is an elastic blade mounted on said distributingshaft.
 5. A cleaning installation according to claim 3, wherein saidoutlets are shaped in said first part and in that said blade forms saidnozzles by remaining in contact with said first part when no cleaningsolution is injected into the channel or when the solution is injectedat a working pressure.
 6. A cleaning installation according to claim 3,wherein each nozzle comprises additional cleaning means for the nozzle.7. A cleaning installation according to claim 6, wherein said additionalmeans comprises a cleaning nozzle sending air under pressure in saidnozzle.
 8. A cleaning installation according to claim 6, characterisedin that it comprises several distributing shafts, each supporting anarray of nozzles.
 9. A printing machine comprising a cleaninginstallation as claimed in claim
 1. 10. A cleaning installationaccording to claim 4, wherein said outlets are shaped in said first partand in that said blade forms said nozzles by remaining in contact withsaid first part when no cleaning solution is injected into the channelor when the solution is injected at a working pressure.